ExRNA: Decoding Messages Between Cells

New Research into Extracellular RNA Could Lead to Better Disease Diagnoses and Treatments

Extracellular RNAs, or ExRNAs, travel in body fluids including fluid surrounding the brain and spinal cord, urine and blood.

RNA has long been known to perform yeoman's duty on the intracellular assembly line, following genetic instructions to help guide protein production.

But it turns out that RNA is not merely an essential and reliable, if unexciting, workhorse. Scientists have discovered a type of RNA that ventures beyond the cell, travels through the bloodstream and could play a vital role in facilitating communication with other cells.

There's still much to be learned about so-called extracellular RNA (exRNA), including what exactly it does and how much power it has to direct or disrupt physiological processes throughout the body. The potential, however, could be enormous: What if testing a person's exRNA sample, like a blood test, could diagnose his or her disease earlier and more accurately? What if exRNA could be programmed and sent throughout the body to instruct diseased cells to become healthy again?

Scientists are jumping on the search for answers, fueled by $17 million in new targeted funding from the National Institutes of Health (NIH). Last August, the NIH announced funding for 24 projects, including two from UC San Francisco that seek to better understand basic exRNA biology.

"We don't know much yet about this new family of exRNAs. But they appear to play both protective and pathogenic roles in health," NIH Director Francis Collins, MD, PhD, wrote shortly before the funding announcement.

Since then, the NIH has made additional awards to advance this new research field. The agency aims to fund the creation of shared databases that catalog all the exRNAs found in the body, as well as their targets – in tissues including blood, saliva, urine, semen, breast milk, amniotic fluid and cerebrospinal fluid. Another goal is to marry this data with clinical research to find associations between exRNA and disease.

"Extracellular RNA is the most recent, and one of the most surprising and potentially far-reaching elements of the RNA world to be uncovered over the past three or so decades," said Keith Yamamoto, PhD, vice chancellor for research at UCSF.

ExRNA's Role as Biomarker and Beyond

Like its cousin DNA, RNA can exist in a near-infinite number of distinct sequences formed by linked nucleic-acid building blocks. This allows for great specificity – different RNA molecules can have different interactions and effects.